1. Field of the Invention
The present invention relates generally to a medical imaging apparatus for biological tissue visualization and assessment and more particularly to a medical imaging apparatus and method for the detection of abnormal biological tissue including cancerous and precancerous cellular regions of arteries for detection of arterial disease.
2. Description of the Related Art
With the pervasiveness of cancer in modem times, it has become common to screen the aeorodigestive tract, gynecological (GYN) tract and breast(s) for malignancies. There are many ways to screen these sites including X-Ray imaging, MRI (magnetic resonance imaging), CT (computer tomography) scanning, and endoscopy. Disadvantages of X-Ray imaging, MRI and CT scanning include time consumption, high cost and harmful radiation exposure. Moreover X-Ray imaging, MRI and CT scanning cannot provide detailed photographic images of surfaces of sampled tissue when desired.
Endoscopy is a well-known method to screen for malignancies and uses an endoscope with an embedded optical fiber (or fiber bundle). A light from a light source is coupled into the fiber or fiber bundle and delivered through the endoscope to illuminate tissue located at a distal end of the endoscope. The light scattered from the tissue is collected by a one or more lenses and either imaged into a detector mounted on the distal end of the endoscope or coupled into an imaging fiber bundle. The image is then transmitted through the endoscope to an imaging means such as a computer or video system for examination by a physician, and for storage, printing, transmission, etc. as desired. During the procedure, if abnormal tissues are visually detected, a medical practitioner can acquire tissue specimens for biopsies and treatment. Moreover, as tissue samples are usually only taken at sites which have visual evidence of a malignancy, the detection of pre-cancerous, or early stage cancerous tissue is delayed, which can have catastrophic results.
Currently, endoscopy is an invasive method of imaging which requires that the patient be anesthetized and which can cause discomfort or pain to the patient after the procedure. Moreover, endoscopy is expensive and time consuming, and cannot immediately confirm the presence of cancer cells or pre-cancerous cells. Furthermore, the removal of tissue specimens for biopsies can cause additional discomfort or pain to the patient after the procedure.
Recently, there have been several advances in the field of endoscopy which were aimed at solving some of endoscopy's disadvantages. For example, a technology using native tissue fluorescence for detection of cancer and precancer cells by exciting a tissue with UV and/or visible light from an optical source (e.g., lasers, LEDs, lamps, etc.) and detecting the emission by photo-detectors has been developed. Because carcenogenesis modifies the molecular and structural properties of cells and tissues, resulting in changes of the cells' and tissues' optical properties, abnormal cells (e.g., precancerous and cancerous cells) can be optically detected. For example, fluorescence signatures from key tissue fluorophores, such as aromatic amino acids, collagen, elastin, reduced nicotinnamide adenine dinucleotide (NADH) and flavins, can accurately and immediately distinguish normal tissues from malignant and pre-malignant tissues. This optical detection method does not require tissue acquisition and subsequent in-vitro biopsies, which greatly reduces patient discomfort and can allow for immediate detection of cancer. The immediate detection of cancer can be life-saving, as any reduction in time in the diagnosis of cancer can reduce the likelihood of the progression of the cancer—especially when dealing with highly malignant cancer. This technology was invented by the inventor of the present invention and is described in U.S. Pat. No. 4,930,516, entitled, “Method For Detecting Cancerous Tissue Using Visible Native Luminescence,”U.S. Pat. No. 5,131,398 entitled, “Method And Apparatus For Distinguishing Cancerous Tissue From Benign Tumor Tissue, Benign Tissue Or Normal Tissue Using Native Fluorescence,” and U.S. Pat. No. 6,091,985 entitled, “Detection Of Cancer And Precancerous Conditions In Tissues And/Or Cells Using Native Fluorescence Excitation Spectroscopy,” all to R. R. Alfano, et al., the contents of all of which are incorporated herein by reference.
Although the use of a point source fluorescence for the detection of cancer has been demonstrated in areas of the body which do not require the use of a endoscope, such as areas of the gynecological (GYN) tract, aerodigestive tract, colon, breast and esophagus, in vivo fluorescence imaging through an endoscope has presented formidable problems such as: currently available imaging endoscopes use imaging fibers manufactured from glass and therefore cannot transmit the required UV and blue light; detectors located on the distal end of endoscopes have poor UV spectral response; and fluorescence signals in UV and blue light are weaker than scattered light and thus require electronic amplification.
Another technology to improve the screening of the aeorodigestive tract employs a remotely controllable micro-scale imaging device as a replacement to endoscopy. This technology has the potential to greatly reduce the invasiveness of endoscopy and to allow access to harder-to-reach organs such as the small intestine. This technology was invented by the inventor of the present invention and is disclosed in U.S. Pat. No. 6,240,312 B1, entitled, “Compact Photonics Explorer,” to R. R. Alfano, et al., the contents of which are incorporated herein by reference.
Unfortunately, the use of fluorescence spectroscopy and imaging in a single micro-scaled device capable of both visually imaging and assessing tissue needs improvement.